Description of the Related Art
In certain land drilling locations a number of wells are drilled from the same surface location, referred to as a “pad.” The wells are drilled directionally to access oil reservoirs that extend horizontally from the pad. In order to optimize the time used to move the rig to the next well on a pad, it is necessary to skid the drilling rig from one well on the pad to another well location on the same pad. The distance between the wells on the same pad varies but can, for example, be in the order of about ten meters.
The land drilling rig used for drilling wells on the pad is comprised of a number of support modules containing such equipment as engines, mud pumps, accumulator, etc. The associated support modules or machinery are typically mounted on steel skids.
In the past, the movement of the drilling rig was facilitated by splitting the module into two different parts. One part (consisting of the substructure, mast, doghouse, transfer mud tank, and catwalk) was the mobile unit that was dragged from well to well. The second part (consisting of mud pumps, generators, electrical, central mud system) was spotted permanently on the pad location. These two parts are linked with the use of suitcases (an umbilical-cord like connection comprised mainly of cables and hoses). Large lease locations, difficulties in transferring gasified mud, the need to construct a pad-specific rig, and unpolished move times suggested the need for improvements.